JPA 10-105053 and 7-262494 disclose map information providing systems of a network type and are referred to hereafter as first and second publications, respectively. With the system disclosed in the first publication, map information is received in predetermined area units in a car, and, before the car moves from the present area to the next area, map information of the next area is received. After the map information of a next area has been received, the map information of the present area is erased. In the system disclosed in the second publication, on the other hand, route information is stored at a center. A terminal transmits information which identifies the present position and a destination to the center. In response to such information, the center transmits main information on the vicinity of the present position to the terminal.
JPA 10-122885 discloses a navigation apparatus and is referred to hereafter as a third publication. According to the apparatus described in the third publication, a travel route is entered in the main unit of a navigation apparatus via a computer for inputting a route. When a vehicle is approaching a branch in the route, the navigation system determines a branch direction based on the entered travel route and the present position.
JPA 7-332993 also discloses a navigation system and is referred to hereafter as a fourth publication. The navigation system of the fourth publication has a means for detecting crossings to be encountered in the future and complicated crossings.
JPA 10-325734 is a fifth publication which discloses a system wherein an operation to enter a desired destination is made simple. According to the fifth publication, there is a proposed technique for searching a word dictionary for candidates for a desired destination by using a wild card entered by the user and displaying the candidates found in the search, making it unnecessary for the user to enter the entire string of characters representing the desired destination.
The Internet also has a page for rendering services by displaying the names of candidates for a location of interest by accepting the literal (written) phonetic transcription of the name or some kanji characters thereof. These Internet services will be referred to as a first Internet technique.
The Internet also provides services which involve the display of a map and the loading of a new map for a predetermined range centering at a coordinate point from a server when it is desired to move a vehicle up or down or in the right or left direction from the present position on the displayed map. The services make use of a scroll button to move the position. These Internet services be referred to as a second Internet technique.
In the system described in the first publication, the entire map of a next area is downloaded when a border of the present map is approached. Thus, there is a problem of the memory running out of space in the terminal. Thus, the system allows the previously used map to be deleted. Since a used map is not erased before the map of a next area is downloaded, however, the problem of an insufficient memory space is not solved. In addition, the map of the next area is downloaded after a border of the present map is approached. It is thus quite within the bounds of possibility that all of the next map can not be downloaded even after the border has been crossed due to, for example, the fact that the map is downloaded while the vehicle is passing through a tunnel. In this case, the user can not see the next map even after the vehicle has entered the next area. Furthermore, there is a case in which, even though the user merely needs to drive the vehicle straight along the present road so that no map is necessarily required, a next map is inadvertently downloaded, raising the communication charge.
In the system described in the second publication, the map of the vicinity of the present positional which the terminal is located is downloaded on the basis of information on the present position. Thus, much like the system disclosed in the first publication, it is also quite within the bounds of possibility that communication is disabled while a next map is being downloaded, making further downloading impossible, so that the user is incapable of referring to the next map. In addition, there is no description of a solution to the problem of an insufficient memory area, leading us to believe that the operation proposed in the second publication is not capable of resolving the problem.
In the case of the system disclosed in the third and fourth publications, since data stored in a data base of the terminal is used, the systems are not capable of keeping up with new updates of a map, such as additional new roads and closed ones. In the case of the system disclosed in the fourth publication, particularly, the location of interest to the user is merely enlarged and displayed on a map, but, since the display itself does not include changes in the location of interest, such as new roads, the user can easily get confused. In addition, an external storage unit is required for storing the map base, raising the cost of the system and increasing the size thereof.
In the case of the system disclosed in the fifth publication, there is a problem in that the number of wild cards may be entered incorrectly in the case of a long string of characters. Other problems include a long search time of a large data base for the name of a location in a server shared by a plurality of terminals, and, hence, a long wait time which makes the user impatient.
The first Internet technique has a problem in that, when the literal (written) phonetic transcription of the name of a place does not exactly match its stored spelling, candidates for the name of the place can not be displayed. Take "Oomikacho, Hitachi-city, Ibaraki Prefecture" as an example of a stored spelling. If the user incorrectly enters a literal input "Hitachi-city Oomika" or "Oomikamura, Hitachi-city", the display for the place will not appear since the lateral input does not exactly match the stored spellings. Thus, the first Internet technique has a problem in that an incorrect human input can not be handled.
As for the second Internet technique, the service of displaying the map of a destination based on picture data entails a large amount of information which takes a long time to download and increases the communication charge.